Will a middle ear infection affect my singing voice?

Usually not: Ear infections usually only affect the ear not the voice. Sometime though the same viral illness can affect more than one area of the body. That is why someone can have for example an ear infection runny nose and diarrhea.

Not by itself: It may affect your ability to hear yourself from that side if needed to adjust your vocals.The structure is so far away from your voice box it will not have a direct influence. However, ear infections often follow or come concurrently with upper respiratory infections that may include these structures.